The goal is to determine mechanisms for abnormal vascular reactivity in diabetes mellitus. The hypothesis is that the hyperglycemic milieu leads to dysfunction of endothelial cells and sympathetic nerves within blood vessels, which then abnormally regulate vascular smooth muscle contraction. Studies demonstrated that the endothelium-dependent relaxation to acetylcholine of diabetic aorta is impaired. The normal relaxation by endothelium-derived relaxing factor is counteracted by the production by diabetic endothelial cells of vasoconstrictor prostanoids including thromboxane Az. The abnormal endothelial cell function is likely due to hyperglycemia, because the endothelium of normal aorta exposed to high glucose concentrations also responds abnormally by producing vasoconstrictor prostanoids. Preliminary studies indicate that cultured aortic endothelial cells exposed to elevated glucose will provide a useful mode in which to identify bioassayable endothelium-derived vasoconstrictor prostanoids. Prostanoids including 6-keto-PGF1a, thromboxane B2, PGF2a, PGE2, and 15-HETE will be measured by radioimmunoassay, and radiochromatography will be used to analyze metabolic products of 14C- arachidonic acid to identify the vasoconstrictors involved. Neuropathic changes were also found in diabetic rabbit arteries with reduced quantities and abnormal release of norepinephrine with reduced prejunctional inhibition by the endothelium. The modulation of endogenous norepinephrine release from adrenergic nerves and metabolism by diabetic endothelium will be investigated. The proposed studies will pursue the physiological mechanisms of the altered endothelial cell and adrenergic nerve function in arteries from diabetic rabbits and normal arteries exposed to high glucose. Evidence will be sought for abnormal aldose reductase activity, myo- inositol levels, g-proteins, protein kinase C, and Na/K ATPase. Because of the importance of microvascular disease in diabetes, new studies are proposed to study reactivity of isolated coronary and mesenteric microvessels, and resistance vessels in perfused hearts.